This invention relates to a process for desulfurizing combustion gas.
The strict regulations limiting in many countries and many regions the emissions of sulfur oxides through the gaseous effluents of heat generators forbid the use of fuels with a high sulfur content which, besides, may show definite economical advantages: it is the case of some coals having certain similarities to lignites, and of petroleum residues stemming from refining processes.
French patent 2,609,150 describes a process for reducing the emissions of sulfur oxides and particularly the ones of sulfur dioxide coming from a heat generator accepting fuels with a high sulfur content. According to this process, a powdered desulfurizing agent is injected into the combustion gases and the resulting mixture is circulated in a desulfurization zone, then the at least partially desulfurated gases are partly separated from the powdered desulfurizing agent which can be recycled or discharged.
A similar process is described in the French patent application EN. 88/12,363. In this patent application, the mixing of the desulfurizing agent particles with the combustion gases is carried out in a turbulence zone located upstream from the desulfurization zone.
With this type of desulfurization, the rate of use of calcic or magnesian absorbents such as calcium and magnesium oxides and carbonates remains limited. The reason for this phenomenon has not been totally cleared up, but it seems that a skin which partly prevents the reagents from getting into the grains, forms at the surface of these grains.
A process allowing to remedy the drawbacks mentioned above and particularly allowing to obtain high desulfurization rates and to increase the rate of use of the absorbent, at a lower cost, has been discovered.